frizzlegooch
Well-Known Member
is 175 cfm for an inline fan enough for a 20 x 36 x 63 inch tent? this shit racks my brain i use metrics.
CFM question help appreciated!
- Thread starter frizzlegooch
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frizzlegooch
Well-Known Member
like is my math correct here? 20 x 36 x 63 = 45360 inches / 12 = 3780 cubic feet. 3780 cf /175 = 21.6 minutes. so it takes 21.6 minutes to completely exhaust that space with that fan? is that correct and / or good?
Ou8aCracker2
Well-Known Member
20/12= 1.66 Feet
36/12= 3 feet
63/12= 5.25 feet
1.66x3x5.25= 26.14 Cubic feet
In order to cool and ventilate you'll want a 6" 440cfm exhaust fan.
36/12= 3 feet
63/12= 5.25 feet
1.66x3x5.25= 26.14 Cubic feet
In order to cool and ventilate you'll want a 6" 440cfm exhaust fan.
SnapsProvolone
Well-Known Member
Lets round to feet.
2x3x5 = 30 cuft.
A 4" fan is fine. That said a 6" with speed control is more flexible.
2x3x5 = 30 cuft.
A 4" fan is fine. That said a 6" with speed control is more flexible.
SnapsProvolone
Well-Known Member
Im assuming 400 watts.
SnapsProvolone
Well-Known Member
True. Centrifugal style only. Those cheap inline boosters are more of a restriction than anything else.
frizzlegooch
Well-Known Member
Yeah ive been rocking a booster for a couple months, it does enough for the heat removal, but i have a feeling once a put a carbon filter on there it will severely impede airflow.
So been looking at centrifugal inline fans. what you guys think about this one?
http://www.amazon.ca/Inline-Axial-B...F8&qid=1393946303&sr=8-25&keywords=inline+fan
Its the cheapest one, and idk if it would fit in my tent... but eitherway i cant afford a carbon filter ill have to make one.
Anyways thanks guys sorry im startin to ramble
So been looking at centrifugal inline fans. what you guys think about this one?
http://www.amazon.ca/Inline-Axial-B...F8&qid=1393946303&sr=8-25&keywords=inline+fan
Its the cheapest one, and idk if it would fit in my tent... but eitherway i cant afford a carbon filter ill have to make one.
Anyways thanks guys sorry im startin to ramble
frizzlegooch
Well-Known Member
Can you explain the relation between the actual volume and why i need 440 cfm for 26.14?
Not trolling i actually dont know
if 26.14 goes into 440 16 times doesnt that mean 16 room changes per minute? that seems a bit much... whereas the 175 would only be 6 a minute.Not trying to overkill it here i dont even think my tent will hold something bigger than 6 inch
SFguy
Well-Known Member
how many times does the air exchange outside??? (sarcasm) more airflow is better.. the 4" will be plenty fine for a area that small.as metasynth said get the 6" though and a variable controller (rheostat) so if you decide later to upgrade you already have a fan that is capable of what you want.
SFguy
Well-Known Member
Can you explain the relation between the actual volume and why i need 440 cfm for 26.14?
Not trolling i actually dont know
Not trying to overkill it here i dont even think my tent will hold something bigger than 6 inch
i think a 6" is overkill at full blast. i have a 2x4x7 tent and the 6" fan is overkill for that! it sucks my walls in hard and greates a major vaccuum
SpaaaceCowboy
Well-Known Member
Another factor not everyone always asks is outside cab temp....I am cooling about the same size cab with an 80 cfm bathroom fan right now...no filter....around 250 watts.....my outside temp is low to mid 60s....inside the plants sit at a comfy 79
4" duct
4" duct
Ou8aCracker2
Well-Known Member
Because you would be accounting for pressure losses due to attaching ducting,any bends in the ducting run and attaching a carbon filter.
Why do you think I constantly tell people to read ventilation 101?!
So you can do your homework and the forums don't get clogged with a bunch of ventilation questions that are all easily answered in the ventilation 101 thread!
Simply put...my 3x3x6 tent has a 400w HPS in it and I exhaust with a 4" 170cfm inline centrifugal exhaust fan (can fan,elicient,vortex,fantech,hurricane,sunleaves) and that keeps my lights on temps in the tent 10°F above ambient temp (temp of the room the tent sits in and pulls it's fresh air from).
So in order to keep my lights on temp in the tent in the optimal range if 75°F to 78°F I have to keep the room my tent sits in and draws fresh air from between 65°F and 68°F....get it?
Here is just one graph from the ventilation 101 thread....it shows wattage of lights denoted by colored lines,and on one side airflow in cfm,at the bottom the tdiff (temperature differential).
If you look at the chart and notice the line that denotes a 400w HID (Aqua/teal line) and then look at the bottom of the graph where the tdiff is denoted at 10°F above ambient and you follow it to the axis where the 10°F tdiff line meets the 400w HID line and then follow that to where the airflow for that required tdiff at that wattage lighting is you'll see that you need 125cfm to 130cfm airflow AFTER all pressure losses.
I don't use a carbon filter and there are no bends in my ducting run but because of pressure losses from simply just attaching ducting I am getting about 125cfm to 150cfm of effective airflow.
Attaching a carbon filter can/will cause about 25% airflow reduction,90° bends in ducting can cause 25% airflow reduction.
Just read the damn thread and look at the damn chart,I posted it for everyones own damn good!
Ventilation 101
Why do you think I constantly tell people to read ventilation 101?!
So you can do your homework and the forums don't get clogged with a bunch of ventilation questions that are all easily answered in the ventilation 101 thread!
Simply put...my 3x3x6 tent has a 400w HPS in it and I exhaust with a 4" 170cfm inline centrifugal exhaust fan (can fan,elicient,vortex,fantech,hurricane,sunleaves) and that keeps my lights on temps in the tent 10°F above ambient temp (temp of the room the tent sits in and pulls it's fresh air from).
So in order to keep my lights on temp in the tent in the optimal range if 75°F to 78°F I have to keep the room my tent sits in and draws fresh air from between 65°F and 68°F....get it?
Here is just one graph from the ventilation 101 thread....it shows wattage of lights denoted by colored lines,and on one side airflow in cfm,at the bottom the tdiff (temperature differential).
If you look at the chart and notice the line that denotes a 400w HID (Aqua/teal line) and then look at the bottom of the graph where the tdiff is denoted at 10°F above ambient and you follow it to the axis where the 10°F tdiff line meets the 400w HID line and then follow that to where the airflow for that required tdiff at that wattage lighting is you'll see that you need 125cfm to 130cfm airflow AFTER all pressure losses.
I don't use a carbon filter and there are no bends in my ducting run but because of pressure losses from simply just attaching ducting I am getting about 125cfm to 150cfm of effective airflow.
Attaching a carbon filter can/will cause about 25% airflow reduction,90° bends in ducting can cause 25% airflow reduction.
Just read the damn thread and look at the damn chart,I posted it for everyones own damn good!
Ventilation 101
frizzlegooch
Well-Known Member
60 ? isnt that like 18 degrees? thats kinda cold so i could see how that would work for you.. if summers coming you might need a little more though.. and is that 250 of HID or CFL?
cfls are so easy to cool...
Anyways my boosters doing fine for heat but smells becoming an issue so im gonna try and use the 5 inch fan and get a reducer hooked to a C filter
frizzlegooch
Well-Known Member
shit gimme a minute to read that . lol
Ou8aCracker2
Well-Known Member
400w of CFL's produces the same heat as 400w of HID....PERIOD!
frizzlegooch
Well-Known Member
damn dude, way to break it down. plus rep for the resources
frizzlegooch
Well-Known Member
i cant apparently , and yeah thats true but id never have a setup involving that much cfl in the same amount of area a 400 bulb occupies.
Ou8aCracker2
Well-Known Member
A 400w HID (or 400w of cfl or t5's for that matter) is only good for a maximum of a 3x3 aka 9 square foot area as that puts you just below the recommended minimum of 50w per square foot.
The most ideal lighting for a growspace that size would be a 600w HID or 600w of cfl's or t5's and that puts you at the recommended maximum of 66w per square foot.Anymore than that and heat is a major PITA to battle and you'll possibly see light bleaching/burn.Also there is no evidence that more light than the recommended minimum and maximum per square foot will gain you more yeild.
A grow us only as strong as it's weakest link.Genetics are an important factor,but even more so important are environment like proper/adequate lighting,adequate ventilation,temps,humidity,feed strength,not over or under watering/feeding,grower skill level,etc.
The most ideal lighting for a growspace that size would be a 600w HID or 600w of cfl's or t5's and that puts you at the recommended maximum of 66w per square foot.Anymore than that and heat is a major PITA to battle and you'll possibly see light bleaching/burn.Also there is no evidence that more light than the recommended minimum and maximum per square foot will gain you more yeild.
A grow us only as strong as it's weakest link.Genetics are an important factor,but even more so important are environment like proper/adequate lighting,adequate ventilation,temps,humidity,feed strength,not over or under watering/feeding,grower skill level,etc.
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